Fix Start free trial link for self-managed instances

What does this MR do and why?

In !194735 (diffs) the new_trial_url helper was renamed to not be confused with route url. There is one more place where this need to be updated:

The new_trial_url helper method in ee/app/views/dashboard/projects/_blank_state_ee_trial.html.haml incorrectly generates a link to the local instance's /-/trials/new route on Self-Managed and GDK installations. This route only exists on GitLab.com, causing a 404 error on all other instances. The link should instead point to the GitLab Customer Portal for Self-Managed trial registration.

Regression identified: This functionality was working correctly in v17.4.1-ee but is broken in v18.3.2-ee.

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How to set up and validate locally

• Apply patch:

570662.patch

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diff --git a/app/helpers/projects_helper.rb b/app/helpers/projects_helper.rb
index 0d6f1d06d5e3..dcc6d82e0e19 100644
--- a/app/helpers/projects_helper.rb
+++ b/app/helpers/projects_helper.rb
@@ -715,6 +715,7 @@ def dashboard_projects_app_data
   end
 
   def show_dashboard_projects_welcome_page?
+    return true
     dashboard_projects_landing_paths = [
       root_path,
       root_dashboard_path,
diff --git a/ee/app/helpers/ee/dashboard_helper.rb b/ee/app/helpers/ee/dashboard_helper.rb
index 8e9cb5b119ff..ec7caacd1d11 100644
--- a/ee/app/helpers/ee/dashboard_helper.rb
+++ b/ee/app/helpers/ee/dashboard_helper.rb
@@ -29,6 +29,7 @@ def user_default_dashboard?(user)
 
     # EE:Self Managed
     def has_start_trial?
+      return true
       !current_user.has_current_license? && current_user.can_admin_all_resources?
     end

• Sign in as root. Visit /dashboard/projects.
• The Start free trial button should lead to CDot portal.

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Related to #570662